Alyssa Roenigk is a senior writer for ESPN The Magazine and ESPN.com whose assignments have taken her to six continents and caused her to commit countless acts of recklessness. (Follow @ESPN_Alyssa on Twitter).

MELBOURNE, Australia -- Moments after winning what will be remembered as one of the greatest slugfests in Grand Slam history, Naomi Osaka stood at center court, shoulder-to-shoulder with Australian Open runner-up Petra Kvitova, and allowed the slightest satisfied smile to slowly lift her cheeks. As the crowd inside Rod Laver Arena stood, cheering and hollering Osaka's name, the shy, humble champion -- who'd just gutted out a two-and-a-half-hour, 7-6 (2), 5-7, 6-4 win -- nodded solemnly in acknowledgment of their praise.

This was the moment Naomi Osaka deserved, a moment befitting a back-to-back Grand Slam champion who, come Monday morning, will become the first Japanese player to reach No. 1.

It was a far cry from the heart-crushing image of four months ago, when cameras immortalized the brutal reality of Osaka's first major win, at the US Open, her black visor pulled low and her hand covering her eyes as Serena Williams' arm was wrapped consolingly around her shoulder.

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On that hot September night, Osaka disappeared into her own trophy celebration as a chorus of boos drowned out any cheers directed her way. What was meant to be an event honoring Osaka instead became a protest about the way in which Williams had lost. Saturday night in Melbourne, Osaka's pink visor remained lifted, and the cheers were thunderous. Osaka was too busy hoisting the Daphne Akhurst Memorial Cup to be concerned with wiping away tears.

"I had dreams that I would win this tournament," Osaka said in her final news conference of the fortnight. "Every time I have a dream, somehow I accomplish it. Still, I feel like it's a very strange moment, like it's not necessarily real."

At this tournament a year ago, it would have been difficult to find someone who would have predicted this day. Were you to walk the grounds at Melbourne Park and poll the average tennis fan, chances are few would have been familiar with the 2016 WTA Newcomer of the Year, the woman ranked No. 72 in the world at the time. One year later, 21-year-old Osaka is the defending US Open and Australian Open champion, the first Japanese player to win a Grand Slam and the first player in 18 years to win her first two majors in consecutive events.

Naomi Osaka and Petra Kvitova played 35 total games, tying the record for the longest Australian Open women's final in the Open era. Scott Barbour/Getty Images

"For me, every practice and match I've played, it feels like the year is short and long at the same time," Osaka said. "I'm aware of all the work I put in. I know all the sacrifices every player does to stay at this level. "In my opinion, [my success] didn't feel fast. It felt kind of long."

With this win, Osaka is no longer The Girl Who Beat Serena in That Crazy US Open Final. She is a full-fledged, boldface, one-name star, even if she is reluctant to acknowledge and embrace her new, selfie-filled reality. "No. I'm not," Osaka said in a postmatch TV interview, deflecting the idea that she has become as recognizable as she is. "I still don't think that is going to happen."

While her indifference is endearing, in reality, it happened months ago. In the wake of her US Open win, the spotlight on Osaka has been hot enough to melt the confidence and self-assuredness of any young athlete. That's not to mention the pressure -- both external and self-inflicted -- that comes with winning a maiden Grand Slam. There's a reason that there have been 14 one-Slam wonders since 1980, that eight different women won the past eight Slams before Osaka and that no woman since Serena in 2015 had hoisted back-to-back trophies.

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For the past few years, and certainly in Serena's absence in 2017, the question of who would step up and take the reins of women's tennis persisted. Would anyone break through, win multiple Slams and step into the role of The Woman to Beat? The answer, until Osaka, was everyone and no one at all. The parity on the women's tour has been exciting, knowing any player could beat anyone else on any given day. But the sport also needs new stars and budding rivalries -- and Saturday's final delivered both. Lucky for tennis fans, it was also likely the first of many great battles to come between the undisputed top two heavyweights in the women's game.

"But the scariest thing about Naomi," TV analyst Jim Courier said on air during the match, "is how much better she can get."

That Osaka was able to defeat the greatest player in the history of the game in her home Slam last September and backup that performance with a gutsy win over a two-time Wimbledon champ speaks as loudly about Osaka's mental toughness as it does about her magic trick of a forehand. What it says about her staying power is yet to be seen.

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Osaka: This last year has been a 'roller coaster ride'

Naomi Osaka describes her journey over the past year after winning back-to-back Grand Slam titles at the US Open and Australian Open.

"When I play my match, everything else is completely not in my mind anymore," Osaka said, in an attempt to explain how she has been able to shut out the noise and expectations in these high-pressure matches. "For me, Grand Slams is something you dream about playing as a kid. I don't ever want to waste this opportunity."